Jesus doesn't just say "Deal with your own sin before you judge others." He just says: "Do not judge."

We do not judge because as disciples of Jesus we know that only God is capable of judgement that is true and good. We do not judge, because we know that God has made the only necessary judgement on sin…in Christ, on the cross. And we do not judge because we too fall short of God’s Kingdom ideals. Instead, recognizing that we live only in the presence and mercy of God’s good gifts to us, recognizing that God's response to my sin was love, forgiveness, and sacrifice...we offer the same to others: love, forgiveness, sacrifice, and a hand up.